Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely new behavior: the invalid_api_key error path and the fact that the offending key is masked in the response, which the annotations cannot express.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Four short, front-loaded fragments with no padding, and the counts/identity payload leads. The telegraphic style is efficient, though the 'how to get one' fragment is a dependency that isn't paid off in the text.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With an output schema present the return shape needn't be spelled out, and the description still covers the optional-parameter case and the error case. Nothing critical for a zero-required, single-param identity call is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% and the api_key field already explains the Authorization: Bearer fallback in detail, so the description does little beyond it. The 'unknown key fails with invalid_api_key' line adds a bit of error semantics, but the baseline of 3 is appropriate given the schema does the heavy lifting.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states the concrete resource and payload: which studio a key belongs to, plus game and pact-request counts, and the failure mode for an unknown key. That is enough to separate it from siblings like create_studio or list_my_games, though it never names an alternative explicitly.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It sketches three key states (no key, existing key, unknown key), which implies usage, but never says when to call this versus create_studio/list_my_games. The phrase 'Without a key, how to get one' also promises guidance the description itself does not deliver.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.